The objectives are to study hypothalamic regulation of AP function, with particular emphasis on control of prolactin, FSH, LH and GH secretion during the estrous cycle, pregnancy, lactation, post-reproductive life (aging) and in development and growth of mammary and pituitary tumors. We hope to define and characterize hypothalamic PIF and PRF in control of prolactin secretion, and study the effects of pure or synthetic PIF and PRF on mammary growth, lactation, mammary tumors and early pregnancy. Hypothalamo-pituitary functions will be evaluated in old female and male rats, attempts will be made to reinitiate reproductive activities, and comparisons will be made of the capacity of the hypothalamus of old and young mature rats to respond to endocrine and non-endocrine stimuli. The possible physiological role of TRH in prolactin release will be evaluated. The effects of different endocrine treatments on turnover of biogenic amines by the hypothalamus will be studied, with the view of further clarifying their role in control of AP hormones. BIBLIOGRAPHIC REFERENCES: C.J. Shaar, J.S. Euker, G.D. Riegle and J. Meites. Effects of Castration and Gonadal Steroids on Serum Luteinizing Hormones and Prolactin in Old and Young Rats. J. Endocr. 66:45-51, 1975. J. S. Euker, J. Meites, and G.D. Riegle. Effects of Acute Stress on Serum LH and Prolactin in Intact, Castrated and Dexamethasone-Treated Male Rats. Endocrinology 96:85-92, 1975.